Spiral spring



Jan. 31, 1933. VAN DEN 'BRQEK 1,895,948

SPIRAL SPRING Filed Feb. 13, 1931 figure 2 figural.

/m/em0/- fiyure. 5.

Patented Jan. 31, 1933 UNITED STATES;

PATENT OFFICE JOHN A. VAN DER BROEK, OF ANN ARBOR, MICHIGAN [SPIRAL SPRING My invention relates to improvements in spiral springs and their use andis designed to eliminate the contact of the various convolutions of such springs, and the consequent friction resulting from such contact, when such springs are stressed.

I'attain this objective by mechanism illus trated in the accompanying drawing, in which Figure 1 is a view of two spiral springs curve-d in reverse directions, the outer endsAA being connected by bar B to which they are rigidly connected. Figure 2 is a view of two spiral springs, curved in opposite directions, superimposed one on the other. Figure 3 is a View of a single spiral spring with the outer end attached to a movable bar as hereinafter described, 1

For the purpose of the description which follows, I define a spiral spring as an elastic bar permanently curved in such a way that a point moving along it, or along its projection on a plane, would revolve about a fixed point, here called the inner end or center, while at the same time departing from that center, and of sufiioient length so that a straight line between that center and the outer curve of the bar will intersect the bar more than once. The outer endof the spring I define as the point where the spiral as above defined ceases, either because of the termination of the bar itself, because of a material change in its direction, or because the spring starts to approach the center instead of de- 7 parting from it. The inner end of the spring I define as the center of the spiral, regardless of whether or not the spring terminates before the center is actually reached.

I have discovered what has heretofore been unknown as a feature of spiral springs, namely, that if the ends of the spring be permitted freedom of motion in radial relation to each other, while at the same time the tangent of the curve at the outer end is held in constant angular relation to the straight line connecting the ends, the spring can be stressed by coiling or uncoiling without causing the several coils of the spring to lose their relative concentricity, and in consequence, without causing the points of the spring along any one radius to come into contact sooner than do the points along other radii. In other words, my discovery is one whereby the friction in the coiling or uncoiling movement of the spring caused by the contact of the several coils of the spring while it is being coiled or uncoiled can be avoided. This tendency of a spring to retain the relatively concentricv position of its coils while under stress can be produced only by permitting a free movement of the two ends in linear relation to each other,

-Wl1ll6 at the same time maintaining the tangent to the curve of the outer end in constant. angular relation to the straight line connecting it with the inner end. Th. freedom of radial movement coupled with the maintenance of constant angular relation of the tangent can be accomplished in. various ways. Figure 1 of the accompany- 1ng drawing, for example, shows two spiral springs curved in reverse directions, the outer ends AA being connected bybar B, to which they are rigidly connected. If, now, these springs be simultaneously stressed b rotating the tangents to the inner ends CC in opposite directions, the radial distances AC and AC will be reduced. At the same time the connecting bar B will maintain the tangents at the points AA in'constantrelation to the radii CA and CA'. Converse- 1y, when the torque at the points C and C. so is decreased andthe springs are allowed to resume their normal shape, the radii CA, G A willincrease in lengthwhile the relation of the tangents at A, A to the radii is maintained constant by the bar B. 35

Figure 2 of the accompanying drawin is another illustration of'the application 0 my discovery. Here two spiral springs X and Y, curved in opposite directions, are superimposed one upon the other. If the innor end of spring X be held fixed, while the tangent to the inner end of spring Y be rotated, the outer end A of spring Y will be caused to move in a circular path. This point is, however, connected to the outer end A of spring X. The movement of the end A caused by the rotation of the inner end of spring Y causes a circular movement of i A, theouterend of springX. The elastic resistance of spring X, however, prevents m0 the free motion of points A and A, and causes both spring X and spring Y to change their normal shape. In other words, the rotation of the center of spring Y causes both spring Y and spring X to be stressed. As this rotating, or stressing, process continues, the outer ends. A..and A continue to move in a curvedipath, hut at the samertimeathey are free to lessen or increase the radial distance between themselves and the centers of their respective springs; Iflthe connection; of the outer ends A and A be of such a nature as to prevent the tangents of thesetivo' ends from moving in relation to each other,

it will also maintain the tangents in constant relation. to the line between them and. the respective. centers.

Another method is a single spring (Figure- 3.),,the outer end, A, of which: is rigidly fas-.-

tenedito.arigid bai; B,-.said .bar being'in con? tact with aiperpendicular pinatthecenter G. Thisbar is free to move againstsuch pin, but is prevented from angular moti on :by another pin, D,.somewhere. outside the periphery of the spring, As this spring. isstressed by. rotating. the: tangent of the inners en.d,.the outer end,A, is prevented. from. movement in-acurvedlpath by. contactotthe bar againstthe two pins mentioned As this contact,. however, does not prevent longitudinal movement. ofthe bar the end A. is free to approachthe innerendorto depart from it, but-the. tangent at A- because of the rigidity ofithe. connection of. the end A and. the bar' ]31willb e maintainedin constant relationto.

the line fromAto G.

Theseillustrations are givenonly for the: sake of. illustration, and. while I. claim.- them specifically,.I do not. limit my claimsto the 405 particular forms thus explained.

Spiral! springs. embodying my invention have. adefiniteadva-ntage over. those not em.- bodying. it,-.in.- this. respectc-When a spiral spring. is put'under stress, either by holding the inner'end ina fixedposition and moving. the outer end-in a curvedpat'h, or by holding the outer. end in such a: way asto prevent. movement in aicurved' path androtating the tangent of? the inner. end in a curved direction, the strain-at. diiferent points: along thecurve of. the bar varies; that is to say, the stress isnot uniformly distributed through out the lengthot thebar. Vhenthisoccurs, it. the ends ofthe spring are-maintained at apermanently" unchanging linear distance. from. each other, the coilstend. to change their. normal unstressed shape in relation to the center, andito lose'their true. spiral con? figuration. Those parts in the line. of. one

radius fromthe center tend to be thrust away fromthecenter, while those parts alongthe opposite radius tend to be thrust. towardthe center. As. this condition. is. exaggerated thosepoints along, the latter. radius. eventually are. broughtinto juxtaposition witheach.

other. As the movement of the coils is continued after these parts have come into contact, a friction between these contact points is created. By my discovery that the tendency of the coils to assume an eccentric position can be markedly lessened by allowing the endsof thespring free movement .in their linean'distance:-ifrom each.o.ther while maintaining the tangent of the outer end in constant angular relation to the straight line conneoting'it with theinner end, I am able practically to eliminate this friction.

Pclaim 1. The. combination of a spiral spring, means for stressing said spring to produce coilingor. uncoiling. of. the. spring. while permittingthe linear. distance :between the ends of'tliespring. to. change, .andYmeans-for maintaining the. tangent tothe. curve. of. the. outer. endof the spring. in constant.relation.tothestraight line betweenit. and. the. inner. end during. such coiling; or. uncoiling; operation.

2. The combination offtwo. spiral springs, means for. stressing. oneor both. of. said.

springs to: produce. coiling or. uncoiling. off

thesprings, and means .for attaching an .end: of one. springto anand-of the-.otherin such. away as to maintain the. ends so attached in constantatangential:relation to eacliotherv while. leavingthem free. to vary their. linear. distance. fiiomthe other ends of the. springs during said coiling or uncoiling operation J OHN A VAN DEN. BBOEKC 

